KMT-2021-BLG-0284, KMT-2022-BLG-2480, and KMT-2024-BLG-0412: Three microlensing events involving two lens masses and two source stars

¹ Department of Physics, Chungbuk National University, Cheongju 28644, Republic of Korea
² Astronomical Observatory, University of Warsaw, Al. Ujazdowskie 4, 00-478 Warszawa, Poland
³ Institute of Natural and Mathematical Science, Massey University, Auckland 0745, New Zealand
⁴ Korea Astronomy and Space Science Institute, Daejon 34055, Republic of Korea
⁵ Max Planck Institute for Astronomy, Königstuhl 17, D-69117 Heidelberg, Germany
⁶ Department of Astronomy, The Ohio State University, 140 W. 18th Ave., Columbus, OH 43210, USA
⁷ University of Canterbury, Department of Physics and Astronomy, Private Bag 4800, Christchurch 8020, New Zealand
⁸ Department of Particle Physics and Astrophysics, Weizmann Institute of Science, Rehovot 76100, Israel
⁹ Center for Astrophysics | Harvard & Smithsonian, 60 Garden St., Cambridge, MA 02138, USA
¹⁰ Department of Astronomy, Tsinghua University, Beijing 100084, China
¹¹ School of Space Research, Kyung Hee University, Yongin, Kyeonggi 17104, Republic of Korea
¹² Department of Physics, University of Warwick, Gibbet Hill Road, Coventry CV4 7AL, UK
¹³ Institute for Space-Earth Environmental Research, Nagoya University, Nagoya 464-8601, Japan
¹⁴ Code 667, NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA
¹⁵ Department of Astronomy, University of Maryland, College Park, MD 20742, USA
¹⁶ Department of Earth and Planetary Science, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
¹⁷ Instituto de Astrofísica de Canarias, Vía Láctea s/n, E-38205 La Laguna, Tenerife, Spain
¹⁸ Department of Earth and Space Science, Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043, Japan
¹⁹ Department of Physics, The Catholic University of America, Washington, DC 20064, USA
²⁰ Department of Astronomy, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
²¹ Sorbonne Université, CNRS, UMR 7095, Institut d’Astrophysique de Paris, 98 bis bd Arago, 75014 Paris, France
²² Department of Physics, University of Auckland, Private Bag 92019, Auckland, New Zealand
²³ University of Canterbury Mt. John Observatory, P.O. Box 56 Lake Tekapo 8770, New Zealand
²⁴ Villanova University, Department of Astrophysics and Planetary Sciences, 800 Lancaster Ave., Villanova, PA 19085, USA

^⋆ Corresponding authors; cheongho@astroph.chungbuk.ac.kr, leecu@kasi.re.kr

Received: 6 August 2024
Accepted: 11 November 2024

Abstract

Aims. We carried out a project involving the systematic analysis of microlensing data from the Korea Microlensing Telescope Network survey. The aim of this project is to identify lensing events with complex anomaly features that are difficult to explain using standard binary-lens or binary-source models.

Methods. Our investigation reveals that the light curves of microlensing events KMT-2021-BLG-0284, KMT-2022-BLG-2480, and KMT-2024-BLG-0412 display highly complex patterns with three or more anomaly features. These features cannot be adequately explained by a binary-lens (2L1S) model alone. However, the 2L1S model can effectively describe certain segments of the light curve. By incorporating an additional source into the modeling, we identified a comprehensive model that accounts for all the observed anomaly features.

Results. Bayesian analysis, based on constraints provided by lensing observables, indicates that the lenses of KMT-2021-BLG-0284 and KMT-2024-BLG-0412 are binary systems composed of M dwarfs. For KMT-2022-BLG-2480, the primary lens is an early K-type main-sequence star with an M dwarf companion. The lenses of KMT-2021-BLG-0284 and KMT-2024-BLG-0412 are likely located in the bulge, whereas the lens of KMT-2022-BLG-2480 is more likely situated in the disk. In all events, the binary stars of the sources have similar magnitudes due to a detection bias favoring binary source events with a relatively bright secondary source star, which increases detection efficiency.